content: /**
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package io.reactivex.common.internal.schedulers;
  
  import java.util.*;
  import java.util.concurrent.*;
  import java.util.concurrent.atomic.AtomicReference;
  
  import io.reactivex.common.RxJavaCommonPlugins;
  
  /**
   * Manages the creating of ScheduledExecutorServices and sets up purging.
   */
  public final class SchedulerPoolFactory {
      /** Utility class. */
      private SchedulerPoolFactory() {
          throw new IllegalStateException("No instances!");
      }
  
      static final String PURGE_ENABLED_KEY = "rx2.purge-enabled";
  
      /**
       * Indicates the periodic purging of the ScheduledExecutorService is enabled.
       */
      public static final boolean PURGE_ENABLED;
  
      static final String PURGE_PERIOD_SECONDS_KEY = "rx2.purge-period-seconds";
  
      /**
       * Indicates the purge period of the ScheduledExecutorServices created by create().
       */
      public static final int PURGE_PERIOD_SECONDS;
  
      static final AtomicReference<ScheduledExecutorService> PURGE_THREAD =
              new AtomicReference<ScheduledExecutorService>();
  
      // Upcast to the Map interface here to avoid 8.x compatibility issues.
      // See http://stackoverflow.com/a/32955708/61158
      static final Map<ScheduledThreadPoolExecutor, Object> POOLS =
              new ConcurrentHashMap<ScheduledThreadPoolExecutor, Object>();
  
      /**
       * Starts the purge thread if not already started.
       */
      public static void start() {
          if (!PURGE_ENABLED) {
              return;
          }
          for (;;) {
              ScheduledExecutorService curr = PURGE_THREAD.get();
              if (curr != null && !curr.isShutdown()) {
                  return;
              }
              ScheduledExecutorService next = Executors.newScheduledThreadPool(1, new RxThreadFactory("RxSchedulerPurge"));
              if (PURGE_THREAD.compareAndSet(curr, next)) {
  
                  next.scheduleAtFixedRate(new ScheduledTask(), PURGE_PERIOD_SECONDS, PURGE_PERIOD_SECONDS, TimeUnit.SECONDS);
  
                  return;
              } else {
                  next.shutdownNow();
              }
          }
      }
  
      /**
       * Stops the purge thread.
       */
      public static void shutdown() {
          ScheduledExecutorService exec = PURGE_THREAD.get();
          if (exec != null) {
              exec.shutdownNow();
          }
          POOLS.clear();
      }
  
      static {
          boolean purgeEnable = true;
          int purgePeriod = 1;
  
          Properties properties = System.getProperties();
  
          if (properties.containsKey(PURGE_ENABLED_KEY)) {
              purgeEnable = Boolean.getBoolean(PURGE_ENABLED_KEY);
          }
  
          if (purgeEnable && properties.containsKey(PURGE_PERIOD_SECONDS_KEY)) {
              purgePeriod = Integer.getInteger(PURGE_PERIOD_SECONDS_KEY, purgePeriod);
          }
  
          PURGE_ENABLED = purgeEnable;
          PURGE_PERIOD_SECONDS = purgePeriod;
  
          start();
      }
  
      /**
       * Creates a ScheduledExecutorService with the given factory.
       * @param factory the thread factory
       * @return the ScheduledExecutorService
       */
      public static ScheduledExecutorService create(ThreadFactory factory) {
          final ScheduledExecutorService exec = Executors.newScheduledThreadPool(1, factory);
          if (PURGE_ENABLED && exec instanceof ScheduledThreadPoolExecutor) {
              ScheduledThreadPoolExecutor e = (ScheduledThreadPoolExecutor) exec;
              POOLS.put(e, exec);
          }
          return exec;
      }
  
      static final class ScheduledTask implements Runnable {
          @Override
          public void run() {
              try {
                  for (ScheduledThreadPoolExecutor e : new ArrayList<ScheduledThreadPoolExecutor>(POOLS.keySet())) {
                      if (e.isShutdown()) {
                          POOLS.remove(e);
                      } else {
                          e.purge();
                      }
                  }
              } catch (Throwable e) {
                  // Exceptions.throwIfFatal(e); nowhere to go
                  RxJavaCommonPlugins.onError(e);
              }
          }
      }
  }
  